Fig. 2: Estimated effects of HEPA filter and household covariates on indoor PM2.5 during the January 2025 fires.
a Summary of indoor PM2.5 (left) and I/O ratio (right) by HEPA filter use across fire phases. Data represent mean values; error bars denote standard errors. Indoor source peaks were removed during analysis (*p < 0.05, **p < 0.01, ***p < 0.001). b Effect of covariates on indoor PM2.5 concentrations during the active fire period (January 7–11, 2025). Forest plot shows estimated linear effects of parametric covariates from the GAM model. Dots indicate point estimates; horizontal lines indicate their 95% confindence intervals (red = p < 0.05, gray = NS, not significant). c Effect of pre-filter status (i) and room clean air delivery rate (CADR) ratio (ii) on indoor PM2.5 concentrations. Points represent GAM model-derived estimates of indoor PM2.5 change (µg/m³) associated with filter characteristics. Horizontal lines indicate 95% confidence intervals. Error bars represent standard errors. Pre-filter status and Room/CADR ratio were modeled separately. NS = not significant (p ≥ 0.05).
